# Author 阳某
f = open("book3", 'r', encoding='utf-8')
f_new = open ("book.bak", 'w', encoding="utf-8")
for line in f:
    if "白鹿原" in line:
        line = line.replace("白鹿原","黑鹿原")
    f_new.write(line)
f.close()
f_new.close()